Uranium Deposits In South China Research Articles

Hydrothermal alteration and element migration in the Egongtang uranium deposit, central Nanling Range, South China

AbstractHydrothermal alteration records fluid–rock interactions and can therefore be used to constrain element migrations during mineralization. Although hydrothermal alteration is widely developed in hydrothermal vein-type uranium deposits in South China, consideration of elemental mass changes during alteration has not been examined. The Egongtang uranium deposit in the central Nanling Range is mainly hosted by the Qingzhangshan granite in South China, and was strongly altered by K-feldspar, quartz, chlorite, illite, haematite, pyrite and carbonates. The alteration section can be divided into five horizontal zones: fresh granite (Zone V), a distal alkaline alteration zone (Zone IV), a chlorite-rich zone (Zone III), a close-to-ore sericite/illite alteration zone (Zone II) and a central mineralization zone with strong haematitization (Zone I). Whole-rock geochemistry of the altered samples indicates that from Zone IV to Zone I, the content of SiO2 and U increases significantly. The mass gains of SiO2, MgO and Fe2O3 were proportional to the concentration of U. The content of trace elements (such as Ba, K, La, Ce, Pr, Sr, P, Eu, etc.) gradually decreases from Zone V to Zone I. The rare earth elements manifest a decrease in light rare earth elements and a slight increase in heavy rare earth elements accordingly from Zone V to Zone I. This study shows that the ore materials of the Egongtang deposit were mainly derived from the Qingzhangshan granites. In the early alkali alterations, large amounts of U were partitioned into the fluids. In the ore-forming stage, ores precipitated accompanied by acid metasomatism such as chloritization, haematitization and carbonation.

The origin of uranium deposits related to the Huangmeijian A-type granite from the Lu-Zong volcanic basin, South China: Constraints from zircon U-Pb geochronology and mineral chemistry

Although most of granite-related uranium deposits in South China are spatially and genetically associated with S-type granites, few are related to A-type granites. In this study, we present whole-rock major and trace elements, zircon U-Pb geochronology, and mineral chemistry data for the Huangmeijiang A-type granite in the Lu-Zong volcanic basin (South China) to investigate the origin of uranium deposits related to this pluton. The uranium ore bodies mainly occur within the Jurassic Luoling formation close to the Huangmeijian pluton. Whole-rock and biotite geochemistry indicates that the F-rich alkaline magmas with relatively high fO2 prompted the partitioning of U into the fluids released from the Huangmeijian pluton with an affinity of A-type granites, which would set the stage for the later concentration of the U into the Jurassic Luoling formation. Thorite, zircon, apatite, and bastnäsite are the dominant accessory minerals that host U in this pluton. Backscattered electron (BSE) images suggest that some zircon and thorite grains can be divided into the unaltered domains and altered domains. The textural features are interpreted as a later hydrothermal event superimposed on the magmatic zircon and thorite. In situ LA-ICP-MS U-Pb dating on the unaltered domains and altered domains of zircon grains yielded weighted mean ages of 127.8 ± 1.0 Ma and 65.7 ± 5.3 Ma, respectively. The former age represents the emplacement age of the Huangmeijian pluton, and the latter one overlaps the timing of a uranium mineralization event (∼66.6 Ma) in this area. The altered domains of thorite and high-(U + Th) zircon grains have lower U contents than those of the unaltered domains, indicating that uranium was mobilized from thorite and zircon during fluid infiltration, which might be the main source of uranium for the ∼ 66.6 Ma uranium mineralization. Our study suggests that the Huangmeijian pluton was the primary source of uranium for the formation of uranium deposits in this area.

General characteristics and research progresses in metallogenesis of granite-related uranium deposits in South China

General characteristics and research progresses in metallogenesis of granite-related uranium deposits in South China

Metallogenic characteristics and genesis of granite type uranium ore bodies in South China

South China is the key producing area of granite-type uranium deposits in China. After decades of exploration, many important progress has been made in the study of metallogenic regularity of granite type uranium deposits in this area. On the basis of previous studies, this paper attempts to sort out the geological conditions and characteristics of diagenesis and mineralization of granite type uranium deposits in South China, and discuss their metallogenic models, so as to better summarize the metallogenic regularity and serve the prospecting and prediction.

Whole-rock and biotite geochemistry of granites from the Miao’ershan batholith, South China: Implications for the sources of granite-hosted uranium ores

Granite-hosted uranium deposits are the most important types of uranium deposits in South China, but the metal sources of these deposits are still poorly constrained. The Miao’ershan batholith (South China) is a natural laboratory to address this issue, as well as to highlight the use of biotite composition as an indicator for the petrogenesis and uranium fertility of granites. Here, we present whole-rock and biotite geochemical data for U-bearing (Zhangjia and Douzhashan) and barren (Xiangcaoping and Paleozoic) granites of the Miao’ershan batholith. Contents of Li, Be, Mn, Sn, In, Nb, Ta, Ga, W, and U in the studied biotites increase from barren to U-bearing granites, while Mg, Ni, Co, V, and Rb display the opposite trend, which may indicate higher degrees of fractionation of the U-bearing granites. An Fe/(Fe + Mg) ratio of 0.65 in biotite appears to be an efficient threshold to discriminate between U-bearing and barren granites. New ternary discrimination diagrams are introduced, based on Li–V × 20–Mn and Sn–Co × 5–Nb, respectively, to aid the recognition of the U-bearing and barren granites. The relatively high whole-rock U concentrations (8.0–38.6 ppm) and low whole-rock ratios of Th/U (0.5–3.2) and REE/U (2.1–13.5) of the Zhangjia and Douzhashan granites favored the crystallization of uraninite. The samples experiencing fluid-wallrock interaction from the Zhangjia granite are characterized by low whole-rock U concentrations of 3.0 to 4.2 ppm and high Th/U ratios of 8.2 to 10.1, suggesting that a significant part of the U has been leached out by oxidizing meteoric waters. This confirms that the granite represents the primary source of U at the Zhangjia uranium deposit.

Highly fractionated granite magmas maybe the main uranium source of granite-type uranium deposits in South China: Evidence from the uranium content of zircon in southern Zhuguangshan granitic composite

Highly fractionated granite magmas maybe the main uranium source of granite-type uranium deposits in South China: Evidence from the uranium content of zircon in southern Zhuguangshan granitic composite

Several progresses in the study of uranium deposits in South China

Several progresses in the study of uranium deposits in South China

Genesis and Metallogenic Process of the Lujing Uranium Deposit, Southwest Jiangxi Province, China: Constraints of Micropetrography and S–C–O Isotopes

AbstractThe Lujing uranium deposit, located in the southeastern part of the Nanling metallogenic province, is one of the representative granite‐related hydrothermal uranium deposits in South China. Basic geology, geochemistry, and geochronology of the deposit have been extensively studied. However, there is still a chronic lack of systematic research on the genesis and metallogenic process of the deposit. Thus, we recently carried out an electron microprobe and stable isotopic analysis. The main research results and progresses are as follows:Uranium minerals in this deposit include coffinite, pitchblende, and uranothorite, and small amounts of uranium exist in accessory minerals in the form of isomorphism. Coffinite, which occurs predominantly as the pseudomorphs after pitchblende, also occurs as a primary mineral and is locally formed from the remobilization of uranium from adjacent uranium‐bearing minerals. The mineralizing fluid was originally composed of a magmatic fluid generated by late Yanshanian magmatism. The high As content of pyrite in ores may reflect the addition of meteoric water, or the formation water (or both), to the magmatic hydrothermal system. The δ34S values vary from −14.4‰ to 13.9‰ (mean δ34S = −3.9‰), showing a range that is similar to nearby Cambrian metamorphic strata and Indosinian granites, indicating that these host rocks represent the source of sulfur; however, the possibility of a mantle source cannot be completely ruled out. According to our new isotopic data and recent Pb isotopic data, we conclude that the uranium in ores was derived by leaching dominantly from the uranium‐rich host rocks, especially the Cambrian metamorphic strata. The δ13CPDB values (−8.75‰ to 1.40‰; mean δ13CPDB = −5.41‰) and δ18OSMOW values (5.45–18.62‰; mean δ18O = 13.02‰) of reddish calcite from the ore‐forming stage suggest that the CO2 in the mineralizing fluids was derived predominantly from the mantle, with a small component contributed by marine carbonates. Based on these new data and previous research results, this paper proposes that uranium metallogenesis in the Lujing deposit is closely associated with mafic magmatism resulting from crustal extension during the Cretaceous to Paleogene in South China.

Construction of Recombinant Bioleaching Bacteria Thiobacillus ferrooxidans with Fluoride-Resistant Activity

Thiobacillus ferrooxidans is an important bioleaching bacterium, widely used in leaching, recovery of low-grade metals and environmental bioremediation. In bio-metallurgy industry, fluoride existing in some hard rock uranium deposits in south China severely affects the bacteria viability and inhibit leaching reproduction. In this study, the flr-4 gene that has strong resistance to fluorine ion in Caenorhabditis elegans, was cloned into pET30a vector and expressed in E. coli BL21. the ability of fluoride resistance in E. coli was increased obviously. To increase the fluoride-resistance of bioleaching bacterium T. ferrooxidans strain 1 (T.f1), the flr-4 shuttle recombinant plasmid pJRD215-flr-4 was constructed and transferred into T.f1 by conjugation. pJRD215-flr-4 was stable in T.f1 with more than 70% retention after 50 generations. Recombinant T.f1 was tolerant to fluorine ions and grew well under fluoride (F-) stress especially at F- concentrations ranging from 10 mg/L to 60 mg/L.

Isotope geochronology, geochemistry, and mineral chemistry of the U-bearing and barren granites from the Zhuguangshan complex, South China: Implications for petrogenesis and uranium mineralization

The Zhuguangshan complex carries some of the most important granite-hosted uranium deposits in South China. Here we investigate the Changjiang and Jiufeng granites which represent typical U-bearing and barren granites in the complex, using zircon U-Pb ages, whole-rock geochemistry, Sr-Nd isotopic and zircon Hf isotopic data, and mineral chemistry, to constrain the petrogenesis and uranium mineralization. LA-ICP-MS zircon U-Pb dating shows that both the Changjiang and Jiufeng granites were emplaced ca. 160Ma. These rocks show high silica, weakly to strongly peraluminous compositions, enrichment in Rb, Th, and U, and depletion in Ba, Nb, Sr, P, and Ti. These features coupled with the high initial 87Sr/86Sr ratios, negative εNd(t) values and εHf(t) values, and the Paleoproterozoic two stage model ages of these two granites suggest that the two granites belong to S-type granites, and the parental magmas of the two granites were derived from the Paleoproterozoic metasedimentary rocks. However, the granitoids show different mineralogical characteristics. The biotite in the Changjiang granite belongs to siderophyllite, marking higher degree of chloritization, whereas the biotite in the Jiufeng granite is ferribiotite, characterized by only slight chloritization. Compared with the Jiufeng granite, the biotite in the Changjiang granite has lower crystallization temperature and oxygen fugacity, but higher F content, and the uraninite has higher UO2 content but lower ThO2 content, and stronger corrosion. The chemical ages of uraninites from both granites are (within error) consistent with the zircon U-Pb ages and are considered to represent the emplacement ages of granites. Chemical ages of pitchblende in the Changjiang granite yield 118±8Ma, 87±4Ma, and 68±6Ma, representing multiple episodes of hydrothermal events that are responsible for the precipitation of U ores in the Changjiang uranium ore field. Our study suggests that the degree of magma differentiation and physicochemical conditions of the magmatic-hydrothermal system are the key factors that control the different U contents of these two granites. The mineralogical characteristics of uraninite and biotite can be used to distinguish between U-bearing and barren granites, and serve as a potential tool for prospecting granite-hosted uranium deposits.

Tectono‐Magmatic Activization and Fractal Dynamics of Ore‐Forming of Hydrothermal Uranium Deposits in South China

Tectono‐Magmatic Activization and Fractal Dynamics of Ore‐Forming of Hydrothermal Uranium Deposits in South China

Mineralogy, geochemistry and ore genesis of the Dawan uranium deposit in southern Hunan Province, South China

The Dawan deposit in southern Hunan Province is one of the large-scale metasedimentary rock-hosted uranium deposits in China. Uranium orebodies occur mainly as big vein type and disseminated veinlet type, and are chiefly hosted within the Cambrian metasedimentary rocks, but some small ore veins can extend into the Jurassic Jinjiling granites. The dominant uranium ore minerals include pitchblende and coffinite. Coffinite often replaces and rims the pre-existing pyrite, and pitchblende occurs as veinlets and disseminated grains filled the fracture zones of metasedimentary rocks. It is suggested that the coffinite was most likely formed by initial reduction of U6+ to U4+ by pyrite from an oxidized Si-rich fluid at an early mineralization stage, whereas the pitchblende may have formed at a later stage in a relatively reduced and Si-poor fluid. Chlorite alteration is widespread and is inter-grown with pitchblende in ores. Electron microprobe analysis reveals that the chlorite belongs to Mg-rich clinochlore, which is different to the Fe-rich chlorite in most granite-hosted and volcanic rock-hosted uranium deposits in South China. The hydrothermal alteration temperatures were estimated to be 189–227°C according to chlorite geothermometer. The ores show similar trace element characteristics to those of metasedimentary wall-rocks, but different from those of the Jinjiling granites. Negative Ce anomalies of the ores indicate an oxidized hydrothermal fluid, which was most likely derived from circulated meteoric water. The εNd(t) values of the ores are lower than those of the Jinjiling granites, but fall into the range of the basement strata. Sulfur isotopic compositions of hydrothermal pyrites vary from −9.5‰ to −7.7‰, similar to those from the wall-rocks, which implies that the sulfur in ore-forming fluids was mainly derived from diagenetic sulfur in the sedimentary strata. Pyrite in ores shows highly radiogenic lead isotopic compositions (206Pb/204Pb=19.684–89.234 and 207Pb/204Pb=15.722–19.683). In a plot of 206Pb/204Pb vs. 207Pb/204Pb, the data show a good linear array and yield an isochron age of 479±69Ma (MSWD=1.6), which is much older than the granites but relatively close to the age of the host metasedimentary strata, indicating that the uranium source was probably derived from the wall-rock strata. It is suggested that the Dawan deposit is a hydrothermally reworked uranium deposit (referred to as the carbonaceous-siliceous-pelitic rock type by many Chinese geologists) with a close relationship with the host metasedimentary rocks. The Dawan deposit has no genetic relationship to the Jinjiling granite, contrary to what was previously suggested, and therefore the exploration in this area should focus on the conjunct occurrence of the Cambrian metasedimentary rocks rich in organic carbon and pyrite and the tectonic faulting which fractured and brecciated the strata.

Fractal Character of Structural Control on Uranium Mineralization in South China

South China is the most important uranium producer in the country. Most uranium deposits in south China are strictly controlled by NE-NNE trending regional fracture structure. Fractal analyses on spatial distribution of uranium deposits and regional fracture structure in south China have been done in this paper. It indicates that the spatial distribution of both uranium deposits and regional fracture structure in south China show fractal character. The fractal dimension D=1.4142 for the spatial distribution of regional fracture structure is significantly greater than the critical value and it indicate a higher ripening degree in the fracture structure evolution and an advantages to fluid flow and uranium mineralization. The fractal dimension D=1.0527 for the spatial distribution of uranium deposits in south China show a lower complexity than regional fracture structure. The fractal spatial distribution of uranium deposits in south China is the result of the evolution of the fractal fracture structure system.

Structural control on uranium mineralization in South China: Implications for fluid flow in continental strike-slip faults

South China is the most important uranium producer in the country. Much of the Mesozoic-Cenozoic geology of this area was dominated by NNE-trending intracontinental strike-slip faulting that resulted from oblique subduction of the paleo-Pacific plate underneath the eastern China continent. This strike-slip fault system was characterized by transpression in the early-mid Jurassic and by transtension from the latest Jurassic through Cretaceous to early Tertiary. Most uranium ore deposits in South China are strictly fault-hosted and associated with mid-late Mesozoic granitic intrusions and volcanic rocks, which formed under transpression and transtension regimes, respectively. Various data demonstrate that the NNE-trending strike-slip faults have played critical roles in the formation and distribution of hydrothermal uranium deposits. Extensive geochronological studies show that a majority of uranium deposits in South China formed during the time period of 140—40 Ma with peak ages between 87—48 Ma, coinciding well with the time interval of transtension. However, hydrothermal uranium deposits are not uniformly distributed along individual strike-slip fault. The most important ore-hosting segments are pull-apart stepovers, splay structures, extensional strike-slip duplexes, releasing bends and fault intersections. This non-uniform distribution of ore occurrences in individual fault zone reflects localization of hydrothermal fluids within those segments that were highly dilational and thus extremely permeable. The unique geometric patterns and structural styles of strike-slip faults may have facilitated mixing of deeply derived and near-surface fluids, as evidenced by stable isotopic data from many uranium deposits in South China. The identification of fault segments favorable for uranium mineralization in South China is important for understanding the genesis of hydrothermal ore deposits within continental strike-slip faults, and therefore has great implications for exploration strategies.

Metallogenesis of Devonian-Carboniferous strata-bound carbonate-type uranium deposits in South China

This paper deals with the geological conditions, mineralization characteristics, genetic types and space-time distribution of the Devonian-Carboniferous strata-bound carbonate-type uranium deposits in South China. These ore deposits are genetically classified as the leaching type and the leaching-hydrothermal superimposed type. These ore deposits are confined mainly to the strata (D2–3, C1) of platform-lagoon carbonate facies. Unique tectonic settings are a vital factor leading to the formation of these uranium deposits. A metallogenetic model for these uranium deposits has been proposed.

Isotope Geological Studies of Granite‐Type Uranium Deposits in South China

Abstract The uranium‐bearing granites in South China can be classified into two types, namely, syntectic type and transformation type. A fairly systematic hydrogen, oxygen, carbon, sulfur isotopic study of uranium deposits related to these two types of granites has been carried out by the authors, and the results show that they have obvious differences in such aspects as ore‐forming and rock‐forming ages, properties of ore‐forming solutions and source of ore‐forming substances. The authors hold that the uranium deposits related to the syntectic type granitoids are intimately connected with magmatism in time and space, whereas the uranium deposits related to the transformation type granites, though spatially linked up with uranium‐bearing granites, should actually owe their formation to extension in the fault block movement in South China.